Method and apparatus for forming workpieces, using a sequence of stationary forming stations

ABSTRACT

A device for machining workpieces which includes a series of stationary machining stations (2, 42, 65, 81) arranged around a circle and a row of workpiece holders (3, 38, 64, 82) which are clamped temporarily in the machining stations (2, 42, 65, 81) and periodically interchanged. To ensure quasi-continuous operation with stationary machine stations (2, 42, 65, 81), an interchanger (5, 19, 44, 60, 87) rotates concentrically about the circle (41) of the machining stations (2, 42, 65, 81), grips the holders (3, 38, 64, 82) in succession and forms a transfer or interchange path (6, 45, 62, 90) for the holders (3, 38, 64, 82) to be interchanged between one machining station (2, 42, 65, 81) and the next. The interchange path contains a number of workpiece holders (27) which differs from the number of machining stations (2, 42, 65, 81) in the region bridged by the interchange path (6).

The invention relates to a method and an apparatus for guiding a closedrow of workpiece holders through a closed sequence of forming stationswhich are arranged in a stationary position in a circular shape and inwhich the workpiece holders are temporarily held in place andperiodically transferred.

In the manufacture of mass products which pass through a row of formingstations, such as, for example, packing containers and paper cups, a rowof stationary forming stations having forming tools is provided in aknown method of this type (FR-B-1,376,657) which forms the basis for thewording of the claims, which forming stations have running along them aconveying member, for example a chain or a rotatable table havingholders for the workpieces, which holders are stopped temporarily in theforming stations for carrying out the forming steps (FR-B-1,376,657).The transfer of the workpieces from one station to the next takes placesimultaneously for all workpieces. As a result, considerable mass forcesoccur which impose limits on the acceleration of the operating sequence.In contrast to such a discontinuous machine operation, there are alsocontinuously working machines in which workpiece holders which arearranged on a chain run around rotary tables on which tools arearranged. In these machines, usually only forming operations of the sametype can be carried out by tools of the same type on each rotary table.A multiplicity of tools must therefore be provided in each case, whenentails considerable expense. However, machines of such a type are alsoknown in which a plurality of different series of tools are arranged ona rotary table and the workpieces are brought in succession intoconnection with various of these tools by the chain which carries theworkpiece holders being run over an external deflection sprocket, thedeflection section being selected to be so large that the workpieceholders, after-passing through the deflection section at the rotarytable, reach a forming station which is of a different type from theforming position passed beforehand (FR-A-2,463,081). Since the tools insuch continuously working machines are always arranged on revolvingrotary tables, they are not suitable for such forming operations inwhich, on account of high precision or the size of the tools or forother reasons, the revolving arrangement of the tool is undesirable orimpossible.

The object of the invention is therefore to provide a method of the typementioned at the beginning which permits a stationary tool arrangementin a continuous mode of operation.

This object is achieved according to the invention in that the formingstations are constantly occupied by workpiece holders except for atleast one empty forming station and the workpiece holders, which arearranged flexibility in a row and the number of which is different fromthe number of forming stations, are transferred in succession by meansof a transfer means, revolving continuously and concentrically to thesequence of forming stations, by first of all one workpiece holder beingtransferred to the empty forming station, by a following workpieceholder being transferred to the forming station occupied beforehand bythe first workpiece holder, etc.

Compared with the known machined described at the beginning in which allworkpiece holders are transferred simultaneously, a considerableapproximation to a continuous mode of operation is achieved by theinvention by the workpiece holders not all being transferredsimultaneously but by their being transferred individually insuccession. The division of the transfer operation into a multiplicityof individual steps allocated to the respective holding positionsreduces the masses to be accelerated and braked in each case to a smallfraction, the continuous advance of the transfer operation from oneholder position to the next providing the precondition for substantialmasses, namely those parts which perform the transfer movement, to beable to be moved continuously.

Compared with the known machines mentioned in the second place, theinvention has the advantage that the tools can be arranged in astationary position without having to give up the advantage of thecontinuous mode of operation.

The kinematic principle utilized by the invention is certainly knownfrom mechanism technology (DE-A-1,750,279); but it was not obvious tothe person skilled in the art, in the search for suitable conveyingprinciples for a row of workpieces opposite a row of forming stations,to look around for the forming stations in the field of mechanismtechnology nor to check the auxiliary elements used in a specific casethere between drive and output for transmitting the movement for theirsuitability as workpiece carriers in forming machines.

The method is conveniently carried out by means of an apparatus which isdistinguished by the fact that a transfer means revolves concentricallyto the circle of the working stations arranged in a stationary position,which transfer means takes hold of the workpiece holders in succession,which workpiece holders are connected like a chain, and forms a transferpath for the workpiece holders to be transferred, from one formingstation to a following forming station, which transfer path contains anumber of workpiece holders (for example twelve, fourteen) which differfrom the number of forming stations (for example thirteen, fifteen) inthe area bridged by the transfer path.

In the practical realization of the invention, the row of workpieceholders is allocated in a flexible form to the rigid, stationary andequi-spaced arrangement of the tools so that this row of workpieceholders can on the one hand come into contact with the row having afixed configuration and can on the other hand be lifted from the latterin the transfer area. In this context, the term flexibility is to beunderstood in the widest sense. That does not mean that the individualholders have to be firmly connected to one another in the longitudinaldirection of the row, although this is advantageous. On the contrary,the flexible row can also be formed by unconnected workpiece holderswhich are each only held in place from position to position by specialmembers. These members can be, for example, on the one hand fixingmembers in the forming stations and on the other hand holding members atthe transfer path, which come into effect when the workpiece holders arereceived by the transfer means, are stored in their sequence and aredeposited again in another forming station. So that the transfer effectcomes about, the number of workpiece holders in the transfer path mustbe correspondingly larger or smaller than the number of forming stationsin the area bridged by the transfer path. If the workpiece holders areconnected like a chain at constant distances apart, the transfer pathmust accordingly be shorter or longer than the arc, bridged by it, ofthe row of forming stations by one pitch of the forming stations orworkpiece holders or a by a whole multiple thereof. Instead, provisioncan be made for the distance between the workpiece holders in thetransfer path to be controlled in such a way as to differ from thedistance in the forming stations. If the workpiece holders are connectedto one another like a chain, the different distance apart according tothe invention can be realized by the connection between the workpieceholders being produced by a guide-link arrangement of variable length,the size of which is determined by an additional controlling cam. Inanother embodiment, which is suitable in particular if the workpieceholders are not connected, the transfer means is provided with a drivedevice for the workpiece holders, which drive device takes hold of eachindividual workpiece holder and subjects it in the transfer means to aconveying movement at a suitable distance from the adjacent workpieceholders and at a suitable speed. Finally, it is also possible to connectthe individual workpiece holders to one another by springs which enablethem, depending on the spatial relationships imposed on them by thetransfer means, to assume a greater or smaller distance from one anotherthan corresponds to the distance between the forming stations. Here, thespring force provides for a uniform distribution of the movement sectionpresent in the transfer means over the number of holder spaces andintermediate spaces located therein. In this way, both a reduction(compression spring) and an increase (tension spring) in the distancesbetween the holders relative to the distances between the formingstations can be achieved. This solution can be combined with positiveguidance of the workpiece holders at least at the end of the transferpath so that the workpiece holders can pass accurately into the formingstations allocated to them.

According to the invention, the transfer path can revolve inside thecircle of the forming stations, The transfer means is therefore locatedpredominantly radially inside the space circumscribed by the supportbody of the forming stations. This results in the advantage that only arelatively small number of workpiece holders are needed. At the sametime, the tools are readily accessible from outside, However, it canalso be advantageous to have the transfer path revolve outside thecircle of the forming stations.

In a particularly advantageous embodiment of the invention, the form ofthe row of workpiece holders is determined by the periphery of a guidecam on which the workpiece holders revolve and which on part of itsperiphery forms the transfer path, while the remaining part follows thecourse of the forming stations in a circular shape, in which case thisguide cam revolves inside the support of the forming stations.

It is often necessary for the workpiece holders to perform a movement(separate from the transfer movement) relative to the tools. If this isconnected with a complicated control system, this control system willoften be allocated to the tool. But if it is of a simple nature, it canbe advantageous to allocate it to the workpiece holders. As a result,the relative movement can be derived from the revolving movement of thetransfer means. This is possible by means of controlling cams whichrotate with the transfer means, while the holers or tools are providedwith control parts which are acted upon by a controlling cam and therebytransmit the movement. If different movements are to be provided atdifferent tools, different controlling cams can also be provided whichhave different basic diameters or vertical position and act only oncertain control members having correspondingly matching position atcertain tools. Whereas lifting movements can be produced by controllingcams, rotary movements can be transmitted by parts rolling on oneanother, e.g. by means of a toothed quadrant which is provided on onepart and interacts with a pinion on the other part.

It can certainly be particularly advantageous in the context of theinvention to derive movements of the tools or of the workpieces from therelative rotation of the two machine parts, but if it is of course alsopossible to provide separate drives which are synchronously controlledin a revolving manner.

Another apparatus for carrying out the method according to the inventionis distinguished by the fact that facing a group of n forming stationsis a group of (n-1) workpiece holders which are individually connectedto the conveyor in such a way that they can be moved in the conveyingdirection by at least the distance between the forming stations andwhose connecting points with the conveyor, revolving concentrically tothe sequence of forming stations, are at a distance from one anotherwhich is greater than the distance between the forming stations by thefactor n/(n-1), and that a control device is provided for transferring aworkpiece holder adjacent to the empty forming station into the emptyforming station, for transferring the following workpiece holder intothe forming station consequently becoming empty, etc.

The arrangement can be circular, in which case the said distances can beassumed to be angular distances. Instead, an at least partly extendedarrangement is also possible in which a preferably closed chain conveyorcarrying the workpiece holders faces an extended row of formingstations. The return side of this chain conveyor can likewise interactwith a row of forming stations, but this is not necessary.

The speed of the conveyor is so great that it moves further during eachtransfer operation by the difference between the distance between theforming stations and the distance between the workpiece holders, and infact in the opposite direction to the direction in which the transferoperations follow one another.

According to the invention, this apparatus can be constructed in such away that the workpiece holders are connected to the conveyor by a springloading them in the transfer direction so that the transfer movementtakes place under the action of this spring. A stop is provided at theforming station empty in each case, which stop retains the workpieceholder which, under the action of the spring, is in the transfermovement. So that the workpiece holder does not prematurely leave thepreceding forming station, appropriate control devices which hold it inplace can be provided there. These control devices can comprise the stopmentioned, this stop being removed at the moment at which the transfermovement is to start, or the workpiece holder being lifted past thisstop by another part of the control device. These are control deviceswhich can be provided at every forming station and can be activated atthe desired moment. However, a revolving tripping means can also beprovided as the control device, which tripping means in each case actson the workpiece holder to be released from a forming station andtransferred or on the means which hold this workpiece holder in place inthe forming station.

The invention is described in more detail below with reference to thedrawing, in which:

FIGS. 1 to 4 show four plan views of different machine configurations,

FIG. 5 shows a detailed plan view of an actual embodiment,

FIG. 6 shows a sectional view of the embodiment shown in FIG. 5,

FIGS. 7 and 8 show plan views of further embodiments, and

FIG. 9 shows a partial plan view of a final embodiment.

In the embodiment according to FIG. 1, an annular support body 1 isprovided which has a row of forming stations 2 with tools on its insidewhich are schematically indicated by semi-circles open to the inside.They move into matching position with workpiece holders 3 which areconnected to one another as a flexible conveyor row by a chain 4 whichis held over the larger part of the periphery on the inside of thesupport body 1 by means not shown, whereas in the part appearing at thetop left in the representation it is lifted therefrom by deflectionsheaves 5 which together form a W-shaped path 6 for the chain 4, whichpath 6 represents the transfer path. The sheaves 5 are mounted on acommon support which is not shown in the drawing and on which theyrevolve in the direction of the arrow inside the support body 1. Thetransfer path 6 contains one holder more than the corresponding circulararc of the support body 1. The drawing illustrates that the deflectionpath is just on the point of lifting a holder 8 out of the associatedforming position 9 of the support body, while another holder 10 is justbeing inserted into a position 11. The penultimate holder 12 in thetransfer path will pass into the position 13, the holder 14 into theposition 15, the next holder into the position 9 just becoming free andtherefore the holder 8 into the following forming position 16. Duringone revolution of the transfer path 6, all holders are transferred intothe next forming position. During the transfer movement, each holderdescribes a hypocycloid having an approximately sinusoidal profile ofthe acceleration without acceleration peaks. That is, the transfermovement takes place smoothly and without jerks.

Whereas FIG. 1 shows an arrangement having only one transfer path, thataccording to FIG. 2 has two transfer paths 17. This means that eachholder 3 of the row of holders is transferred twice per revolution. Therow of holders is carried by the periphery of a rotor 19 which revolvesin the direction of the arrow. Each transfer path 17 contains fourworkpiece holders, while the bridged arc of the support body 1 comprisesonly three forming stations in each case. This means that the workpieceholders in the transfer path have to be brought closer to one another.In the example indicated on the right in the figure, they are connectedto one another by compression springs which are compressed in the areaof the transfer path. In the example indicated on the left-hand side,the workpiece holders are provided with spacer discs 20 which determinetheir mutual minimum distance apart and thereby provide for a definedposition of the workpiece holders in the transfer path. This isnecessary so that the workpiece holders can move in a trouble-freemanner into the forming position intended for them without thisnecessitating complicated guide or drive devices.

The exemplary embodiments according to FIGS. 3 and 4 show the outerrevolution of a chain 24 of workpiece holders 27 around the stationarysupport body 25. According to FIG. 3, the length of the transfer path 26is to be three holder distances longer than the corresponding circulararc of the support body 25. The workpiece holders 27 are thereforeshifted three steps further during each revolution. The support body 25has fourteen forming stations, which are designated by the letters a too and are occupied by a workpiece holder 27 in their alphabetical order.If there were fifteen positions instead of fourteen, three groups offour forming stations each would be formed on the support body, and eachworkpiece holder 27 would in each case pass through only one group ofthe three groups. If there are a small number of forming steps, this canbe convenient in order to correspondingly increase the output. If,however, the workpiece holders are to pass through all forming stationsof the support body and the transfer difference is greater than oneholder, the number of holding stations at the support body cannot bedivided by the transfer difference.

The arrow in FIG. 3 indicates that the transfer paths 26 are to revolvearound the support body 25.

FIG. 4 shows a modification of FIG. 3 having two transfer paths 26 atthe periphery which are offset by 180° relative to one another. Thisresults in identical cycle times. If different cycle times are desired,different angular offset can be selected.

In the exemplary embodiment in FIGS. 5 and 6, the machine frame,consisting of bottom plate 30, top plate 31 and connecting columns 32,forms a central, coaxial bearing arrangement 33 for the shaft 34, whichis continuously driven in the direction of the arrow by the motor 55 viagearing 54. The shaft carries the rotor 35, which is formed by theplates 36 and 37 which are fastened to the shaft 34 and, as shown inFIG. 5, have an approximately semicircular, rounded-off outline. Guidedthereon are the workpiece holders 38, which comprise guide bodies 39which slide on the periphery of the plates 36, 37 and are connected toone another by a roller chain 40. The guide bodies 39 have peripheralrecesses in which the margins of the plates 36, 37 engage. Arranged onthe frame at the same height as the plate 36 is an annular plate 41which has peripheral recesses 42 which serve to accommodate the guidebodies 39. A guide body 39, which on the one hand sits in such aperipheral recess 42 and on the other hand is held therein by the margin43 of the plate 36, is positioned in a well-defined manner. It is liftedout of this position as soon as the corner 44 of the rotor 35 or of theplates 36, 37 reaches it. The flexible conveying row held together bythe chain 40 is then lifted from the annular plate 41 and directed intothe transfer path 45. When a guide body 39 reaches the further corner 46of the motor, it is re-inserted into peripheral recess 42 of the annularplate 41.

Each guide body 39 contains a guide rod 47 which carries at the top enda mounting mandrel 48 for a paper cup blank 49. At the bottom end, itcarries a roller 50 which interacts as a follower with a controlling cam51 connected to shaft 34 of the rotor in such a way as to be fixed interms of rotation. The guide rod 47 is pushed into its bottom positionby a spring 52. This arrangement results in each mounting mandrel 48being lifted by the controlling cam 51 as soon as the associated holderis inserted into a forming position.

Allocated to the recesses 42 of the annular plate 41 are tools 53 whichmove into forming engagement with the paper cup 49 due to the liftingmovement just described of the mounting mandrel 48. In so far as theseare tools which come into engagement with the mounting mandrel 48 or thepaper container 49 carried by it only by axial relative movement, as isthe case with the forming of the flanged edges, they can therefore be ofvery simple design.

In the exemplary embodiment according to FIGS. 5 and 6, the transferpath comprises five holders, while the associated circular arc of thesupport plate (annular plate 41) has seven holding recesses 42. Thedifference is two. The support body has sixteen holding positions, thatis, an even number. This means that each workpiece holder 38 interactsonly with the eight holding positions of one of two groups of holdingpositions of the support body. In the case of eight forming steps perworkpiece, this results in a doubling of the output compared with amachine having only eight forming stations of the support body.

A machine of the type shown in FIGS. 5 and 6 can be used, for examplefor forming the base of a paper cup, in the following way:

    ______________________________________                                        Holding position I:                                                                              Base feed                                                  Holding position II:                                                                             Feed of the cup shells                                     Holding position III:                                                                            Hot-air treatment of the                                                      base area, 1st phase                                       Holding position IV:                                                                             Hot-air treatment, 2nd                                                        phase                                                      Holding position V:                                                                              Flanging                                                   Holding position VI:                                                                             Pressing the base                                          Holding position VII:                                                                            Cup lifting                                                Holding position VIII:                                                                           Cup discharge                                              ______________________________________                                    

Appropriate devices can be used for the roll forming of the mouth of thecup.

In the embodiment according to FIG. 7, the workpiece holders 64 arepulled radially outwards by springs 67 or the like, the other end ofwhich is fastened to a ring 69. They are thereby pulled into the holdingpositions 65 of a fixed ring 66 which carries the tools at these holdingpositions. On a rotor 71, a guide rail 60 revolves concentrically to thering 66, which guide rail 60 forms the transfer path 62 by virtue of thefact that it lifts with its leading end the workpiece holders 64 out ofthe holding positions 65 against the spring force 67 and releases themagain at its trailing end for insertion into the nearest holdingposition 65. Here, the length of the transfer path in the example shownis shorter than the corresponding circular arc of the ring 66 by twoholders or holding positions. In other words, in the example given, theworkpiece holders 64 are shifted further by two holding positions 65during every revolution of the guide rail 60 at the ring 66. Thistransfer movement can be followed by the ring 69, since it can rotatefreely along with the guide rail 60. Furthermore, it is a characteristicof this design that a fixed connection between adjacent workpieceholders 64 is not necessary. There can be a chain 70, but it can beadvantageous to dispense with it. However, so that the workpiece holdersperform a uniform movement in the transfer path and their arrival at acertain holding position 65 is ensured, it is convenient to equip themwith spacers, i.e. devices which predetermine their minimum distanceapart. This minimum distance apart need not conform to the mutualdistance between the holding positions 65 but can be smaller.

Instead of the springs 67 which pull the workpiece holders 64 outwards,devices can be provided which push the workpiece holders 64 outwardsfrom the centre or an area close to the centre.

In the example in FIG. 8, the annular support body 80 forms recesses 81as forming stations for workpiece holders 82, which form a closed chainsince they are each connected to one another by two guide links 83, 84which contain articulations at both the workpiece holders 82 and thesecond connecting point 85. The articulation points 85 are guided by aninner guide ring 86 concentric to the support body 80, the guide surfacebeing circular, at least in that arc in which the workpiece holders 82lie in the forming stations 81. It is convenient to design this surfaceto be entirely circular, since it can then be arranged in a stationaryposition. Otherwise, it is connected for common rotational movement tothe guide rail 87, which in this exemplary embodiment, together with theguide ring 86, forms the transfer means.

At its ends 88, the guide rail 87 has a centre distance which is atleast just as large as that of the workpiece holders 82 sitting in theforming stations 81 or of a part which is connected to the workpieceholder and interacts with the guide rail, so that the workpieces, duringtheir revolution in arrow direction 89, can be lifted to the inside outof the mounting recesses of the forming stations 81. During theremaining course, the guide rail 87 has a centre distance which is lessthan that of the support body 80 so that the lifted-out workpieceholders can be directed past the latter.

Whereas outside the arc encompassed by the guide rail 87 the radialdistance between the support body 80 and the inner guide ring 86 isconstant and so large that the zigzag-shaped arrangement of the guidelinks 83 corresponds to the peripheral distance between the formingstations 81, the radial distance between the inner guide ring 86 and theguide rail 87 is less between the ends 88 of the latter. This results inthe zigzag-shaped arrangement of the guide links 83 being extended andthus in the peripheral distance between the workpiece holders 82 beingincreased, and in fact exactly in such a way that a whole number less ofworkpiece holders 82 than forming stations 81 is contained in the arccovered by the guide rail 87. In the example shown, the difference comesto two, the total number of the forming stations being even. Thismeans--just as in the example in FIG. 7--that there are two tool rows,each workpiece passing through only one of the two rows.

An important advantage of the embodiment according to FIG. 8 consists inthe fact that a transfer route 91 for the workpiece holders can bedefined by the course of the transfer path 90 between the guide rail 89and the inner guide ring 86, which transfer route 91 is ideally shortand low in acceleration. It will be recognized from the course of thetransfer route 91 that this transfer route 91 is substantially shorterthan the route 92 which results from the use of the apparatus accordingto FIGS. 5 and 6.

It goes without saying that the apparatus could also be constructed witha transfer route in which the distances between the workpiece holdersare not larger but smaller than in the rest of the revolving area,namely by the distance between the guide surfaces of the inner guidering 86 and the outer guide rail 87 being not reduced but increased.This is possible in the case of an external support body 80 by drawingin the guide surface of the inner guide ring 86 in the area of the guiderail 87 and is obtained in the case of an internal support body 80having a guide rail 87 revolving on the outside by the radial expansionof the latter in the transfer area.

In the last embodiment according to FIG. 9, the preferably stationarysupport 101 for a group of seven forming stations 102 which extend over180° of the circular arrangement will be recognized. An arrangementconforming thereto is located on the other side (not shown) of thearrangement. But the arrangement can of course also extend over the fullcircle.

Provided concentrically to the support 1 is a disc 103 which is drivenin arrow direction 104. Via arms 105, it carries workpiece holders 106,of which there are six in the arrangement shown which are allocated tothe seven forming stations 102. Accordingly, one forming station 107 isalways empty and is ready for receiving a workpiece holder 108 to betransferred which is located in the forming station 109 located in frontthereof.

The arms 105 are guided with pins 110 in elongated holes 111 of the disc103 in such a way that they can assume different positions in theperipheral direction on the peripheral line of the forming stations 102,which positions lie at a distance apart corresponding to at least at thedistance between the forming stations 102. Furthermore, a compressionspring 112 is arranged between the disc 103 and each of the arms 105 insuch a way that the workpiece holders 108 can be acted upon bothradially outwards and in the direction 104 of rotation of the disc, thatis, in the transfer direction. The workpiece holders 106 are held inplace in the forming stations 102, which are constructed as recessedportions, by the spring force (and if need be by further means not shownin the representation).

To transfer a workpiece holder 108 into the empty forming station 107,this workpiece holder 108 must therefore be lifted out of the formingstation 109. For this purpose, a revolving cam 113 is provided whichrevolves in arrow direction 114, and in fact once during each machinecycle, as a result of which the transfer movement is initiated for allworkpiece holders, one after the other.

The cam 113 acts in each case on that workpiece holder which is nearestto the forming station 107 empty in each case. The mounting of the cam113 in the disc 103 is then also in each case approximately in alignmentwith the empty forming station 107. The cam 113 acts on the pin 110 insuch a way that the latter, as indicated by chain-dotted lines for theworkpiece holder 108, is lifted towards the centre against the action ofthe spring 112, as a result of which the workpiece holder 108 is liftedpast the stop 115 which limits the recessed portion of the relevantforming station 109 on the transfer side. Under the action of the spring112, the arm 105 can now shift with the workpiece holder 108 to theempty forming station 107 until the workpiece holder is stopped by thestop 115 located there and is pressed by the spring into the recessedportion of the forming station.

It goes without saying that active drive members which are controlled inthe operating cycle could also take the place of the springs 112, andthat the lifting function of the cam 113 with regard to the pins 110could also be replaced by a device which is in each case provided at theindividual mountings and is individually controlled. Furthermore, it maybe noted that the connection between the workpiece holders 106 and thedisc 103 by the arms 105 is not necessary if provision is made inanother manner for suitable guidance of the workpiece holders. The termconveyor used in the claim is therefore to be understood in the widestsense.

I claim:
 1. Method of guiding a closed row of workpiece holders througha closed sequence of forming stations which are arranged in a stationaryposition in a generally circular shape and in which the workpieceholders are temporarily held in place and are periodically transferred,wherein the forming stations are constantly occupied by workpieceholders except for at least one empty forming station, and the workpieceholders, which are arranged flexibly in a row and the number of which isdifferent from the number of forming stations, are transferred insuccession by a transfer means which revolves continuously andconcentrically relative to the sequence of forming stations, and whereineach workpiece holder is transferred individually to an empty formingstation, and a following workpiece holder is transferred to the emptyforming station formerly occupied by the previously transferredworkpiece holder.
 2. Apparatus for forming workpieces, comprising aplurality of stationary forming stations arranged along a circle and aclosed row of workpiece holders which are temporarily held in place inthe forming stations and are periodically transferred, wherein atransfer means is provided which revolves concentrically to the circleof the forming stations, takes hold of the workpiece holders insuccession, and forms a transfer path for the holders to be transferred,from one forming station to a following forming station, which transferpath contains a number of workpiece holders which differs from thenumber of forming stations in the area bridged by the transfer path, andwherein the row of workpiece holders revolves around a guide cam whichon part of its periphery forms the transfer path.
 3. Apparatus accordingto claim 2, wherein the workpiece holders are evenly spaced from eachother and the transfer path is shorter or longer than the circularlyarranged row of forming stations by one pitch of the forming stations orby a whole multiple thereof.
 4. Apparatus according to claim 2, whereinthe distances between the workpiece holders in the transfer path differfrom the distances between the forming stations.
 5. Apparatus accordingto claim 2, wherein the transfer path revolves inside the circle of theforming stations.
 6. Apparatus according to claim 2, wherein thetransfer path revolves outside the circle of the forming stations. 7.Apparatus according to claim 2, wherein at least one workpiece holder isconnected to a spring.
 8. Apparatus according to claim 2, wherein therelative movement of tools or workpiece holders is controlled by acontrol member comprising a controlling cam revolving with the transfermeans.
 9. Apparatus according to claim 8, wherein the control membercomprises a plurality of controlling cams having at least one of adifferent basic diameter and a different vertical position.
 10. Anapparatus for forming workpieces, comprising:a plurality of stationaryforming stations disposed in a generally circular arrangement, aplurality of workpiece holders connected in a closed chain-type manner,the number of workpiece holders differing from the number of workingstations, and transfer means revolving continually and concentricallyrelative to the circular arrangement of stationary working stations, thetransfer means forming a transfer path along which each of the workpieceholders is transferred individually in succession from one workingstation to a following working station when the following workingstation becomes vacant.
 11. A method according to claim 1, wherein therow of workpiece holders revolves inside the closed sequence of formingstations, and each workpiece holder interacts with only one-half of theforming stations.
 12. An apparatus according to claim 2, wherein theclosed row of workpiece holders is disposed inside the circle of formingstations and each workpiece holder interacts with only one-half of theforming stations.
 13. Apparatus for forming workpieces, comprising aplurality of stationary forming stations arranged along a circle and aclosed row of workpiece holders which are temporarily held in place inthe forming stations and are periodically transferred,wherein a transfermeans is provided which revolves concentrically to the circle of theforming stations, takes hold of the workpiece holders in succession, andforms transfer path for the holders to be transferred from one formingstation to a following forming station, which transfer path contains anumber of workpiece holders which differs from the number of formingstations in the area bridged by the transfer path, and wherein theworkpiece holders are connected by a guide-link arrangement having avariable distance between the workpiece holders, the size of whichdistance is determined by a controlling cam.
 14. Apparatus for formingworkpieces, comprising a plurality of stationary forming stationsarranged along a circle and a closed row of workpiece holders which aretemporarily held in place in the forming stations and are periodicallytransferred,wherein a transfer means is provided which revolvesconcentrically to the circle of the forming stations, takes hold of theworkpiece holders in succession, and forms transfer path for the holdersto be transferred from one forming station to a following formingstation, which transfer path contains a number of workpiece holderswhich differs from the number of forming stations in the area bridged bythe transfer path, and wherein at least one workpiece holder isconnected to a spring.
 15. Apparatus for forming workpieces, comprisinga plurality of stationary forming stations arranged along a circle, aclosed row of workpiece holders which are arranged on a conveyor and aretemporarily held in place in the forming stations and are periodicallytransferred by movement of the conveyor, and a transfer means whichrevolves concentrically to the circle of the forming stations, takeshold of the workpiece holders in succession, and forms transfer path forthe holders to be transferred from one forming station to a followingforming station,wherein facing a group of n forming stations is a groupof (n-1) workpiece holders which are individually connected to theconveyor in such a way that they can be moved in the conveying directionby at least the distance between the forming stations and whoseconnecting points with the conveyor, revolving concentrically to thesequence of forming stations, are at a distance from one another whichis greater than the distance between the forming stations by the factorn/(n-1), wherein a control device is provided for transferring aworkpiece holder adjacent to the empty forming station into the emptyforming station and for transferring the following workpiece holder intothe forming station consequently becoming empty, the control devicecomprising a tripping means at the forming station which the workpieceholder is to leave and a stop at the forming station which the workpieceholder is to reach, and wherein the workpiece holders are connected tothe conveyor by a spring loading them in the transfer direction. 16.Apparatus according to claim 15, wherein the conveyor which is providedfor the workpiece holders is arranged in a circular shape, the distanceis between adjacent workpiece holders being measured as angulardistances.
 17. Apparatus according to claim 15, wherein a revolving camis provided as the tripping means.
 18. Apparatus according to claim 11,wherein the transfer means is provided with a drive device for theworkpiece holders.